Since I'm not going to be working on much for a little while I figure it's no disservice to cover something that actually works.
I picked up a pair of these telecommunications mixers several years back. Three microphone input channels under heavy noise gates and a feedback snubbing ducking stage, feeding an array of in/out connections that also drive the ducking circuitry. These do appear to operate on the "that what is loudest must pass" philosophy. No doubt this facilitated the ability of executives to interrupt one another hundreds or thousands of miles away.
Beyond the Aux input and PA output, the connection block at left is direct line input and output, the only level adjustment is set and forget gain scheduling accessed at the interior of the unit. The middle block is the telecommunications interface, presumably the built in loops only affect the in/out of the transmit/receive trunk. The bandwidth logic and array of other unconventional connections remain, for the moment, shrouded in mystery.
Mind you, I've got a bit of a handle as to the function of say "bandwidth logic", but even armed with the manual I'm taking it slow. For example, in contemplating the two connectors above I realize "TO IN" seems to mean "output" and "FROM OUT" sort of equates to an "input"; but then, in a nanosecond I re-read that as TO/IN and FROM/OUT. TO and FROM have no business being printed on the device itself, save the application trajectories for the installation manual.
I recall once, in the early 1990s of being invited over to a co-workers house to assist in troubleshooting his home stereo, which was non-functional. He had it wired IN to IN and OUT to OUT. Drawing from this memory, I realize I may be overthinking the connector block above, and yes, I do know full well that I should be able to determine direction in about 6 seconds of actual application.
Being pragmatic about the device would rob me of the satisfaction of bellyaching about its inherent obfuscation, and how else am I going to work big words into my discourse? Okay, I'll stop being a bore now.
ATE! They made the brakes for my Volkswagen. I know I am in good hands, even if that transformer is not interleaved.
What? I forgot to mention that being a telecommunications device, superior bandwidth is not a concern. This thing is purposed to plug into telephone lines and screechy little conference speakers. LoFi, eat your heart out. It does actually pass more bandwidth than 300-3400 hz, I have proof, but printed spec does fall short of 20-20K.
Here's a bunch of stuff that makes it work, that's where the magic smoke lives.
Sorry, seems I'm marginally loopy today, and it's time I scramble off to work..